<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>行高问题</title>
    <style>
        body{
            /*line-height: 1.5;*/
            /*line-height: 150%;*/
            font-size: 20px;
            line-height: 1.5em;
        }
        p{
            font-size: 50px;
            background-color: blue;
        }
        h3{
            font-size: 50px;
            background-color: #cccccc;
        }
        div{
            padding:30px;
            line-height: 20px;
            background-color: blue;
        }
        span{
            font-size:30px;
            line-height: 50px;
            background-color: #cccccc;
        }
    </style>
</head>
<body>
<p>你好</p>
<h3>你好</h3>
<div>
    <span>你好</span>
</div>
</body>
</html>